Glossary and Terms#

.exe#: An “.exe” file, short for “executable,” is a common file extension in Windows operating systems and some other computing environments. An executable file contains a program or application that can be run or executed by a computer’s operating system.
.usd#: Universal Scene Description (Binary): This is the standard binary file format for USD. It stores the 3D scene and asset data in a compact, binary form, making it efficient for storage and processing.
.usda#: Universal Scene Description (ASCII): This format stores USD data in a human-readable, ASCII text format. It’s primarily used for debugging and as a reference because it’s easier for humans to read and modify. However, it’s less efficient in terms of file size and loading speed compared to the binary format.
.usdc#: Universal Scene Description (Crate): This is a binary format for USD, optimized for high-performance data storage and retrieval. .usdc files are typically used as the primary format for asset storage and production pipelines, offering faster loading and saving times compared to .usd files.
.usdz#: Universal Scene Description (ZIP): A compressed container file in the ZIP format that can contain both geometry and texture information.
Anisotropic Roughness#: This term describes surface roughness that varies based on the direction of measurement. Unlike isotropic roughness, which is uniform in all directions, anisotropic roughness indicates that the micro-surface irregularities on an object’s surface have a directional preference.
Anisotropy#: This refers to a property of materials or surfaces that causes them to exhibit different reflective or shading characteristics in different directions. Anisotropic materials have direction-dependent behavior, appearing shinier or more reflective in one direction while exhibiting different properties in other directions.
Barycentric Coordinates#: These are a set of coordinates used to describe the position of a point within a triangle or other convex polygon. Defined relative to the vertices of the polygon, these coordinates are useful for various operations in graphics rendering, including interpolation and texture mapping. Barycentric coordinates are represented as a set of weights for each vertex of the polygon.
Bitangent#: This is a vector that is perpendicular to both the surface normal and the tangent vector of a 3D surface at a particular point. Bitangent vectors are typically used in advanced shading techniques, such as normal mapping and bump mapping, to complete a local coordinate system known as the tangent space.
Blue Noise#: This refers to a type of noise pattern with unique properties that make it useful for various applications, including texture mapping, sampling, and anti-aliasing. Blue noise is characterized by a distribution of points or values that are more evenly spaced and have a more perceptually uniform distribution of energy in the high-frequency spectrum, especially in the “blue” region of the spectrum.
Composite Output#: This refers to the final image generated by combining and blending various graphical elements or layers. This process typically involves taking multiple rendered images, often with transparency information, and compositing them into a single cohesive image representing the final scene as it will be displayed to the viewer.
Cone Radius#: This refers to the radius of the cone shape used to represent the path of a ray of light as it extends from the camera into the scene. It helps determine which objects or surfaces in the 3D environment the ray intersects.
DDS File#: DDS stands for “DirectDraw Surface.” It is a file format commonly used in computer graphics and game development, specifically designed for storing and efficiently accessing texture and image data.
Diffuse Albedo#: This refers to the inherent color or reflectance of a surface when it interacts with and scatters incoming light uniformly in all directions. It represents the base color of a surface under diffuse lighting conditions, where there are no specular highlights or reflections.
Disocclusion#: This refers to the process of determining what is visible and what is not in a 3D scene from a given viewpoint. It primarily relates to the handling of objects, surfaces, or portions of objects that were previously hidden or occluded by other objects but have become visible due to changes in the camera’s position or orientation.
DLSS#: NVIDIA DLSS (Deep Learning Super Sampling) is a neural graphics technology that enhances performance by using AI to create entirely new frames and display higher resolution through image reconstruction. It aims to deliver high-quality images and responsiveness.
Emissive Radiance#: This refers to the radiant energy emitted from a surface or object in a 3D scene. It represents the light or color that a surface emits, as opposed to reflecting or scattering light like most materials.
Exposure Histogram#: This is a graphical representation that provides a visual summary of the distribution of pixel brightness or luminance values in an image. It shows how many pixels fall into different brightness or exposure levels, typically displayed as a histogram chart.
Froxel#: This is a portmanteau of “fragment” and “voxel” used in computer graphics. It represents a small 3D volume element or pixel-sized voxel within a three-dimensional space. Froxels are typically used in volume rendering and ray tracing techniques to sample and process data within a 3D volume, similar to how pixels sample a 2D image.
HitT#: Hit-Testing (also called hit detection, picking, or pick correlation) is the process of determining whether a user-controlled cursor (such as a mouse cursor or touch-point on a touch-screen interface) intersects a given shape, line, or curve drawn on the screen.
Inf/Nan Check#: This refers to a process or technique used to identify and handle numerical values that are either infinite (Inf) or not-a-number (NaN) during rendering or computation.
Interpolated Normal#: This is a normal vector calculated for a specific point on a 3D surface by interpolating or blending the normals of nearby vertices. Interpolated normals are used to determine how light interacts with the surface and are crucial for achieving smooth shading and realistic lighting effects.
Isotropic Roughness#: This refers to a property that describes the degree of micro-surface irregularities or roughness on a 3D object’s surface in a uniform and non-directional manner. This roughness affects how light scatters and interacts with the surface, resulting in diffuse reflections.
Local Tonemapper Luminance Output#: This refers to the output of a local tonemapping process, which adjusts the brightness and contrast of an image on a pixel-by-pixel basis. This adjustment is based on the luminance or brightness values of the pixels in the image.
Material Type#: This refers to a classification or categorization of the physical properties and visual characteristics of surfaces or materials used in 3D scenes. Material types describe how light interacts with a particular surface and how it should be shaded and rendered. Common material types include diffuse materials, specular materials, translucent materials, and emissive materials.
Normals#: These are perpendicular vectors on the surfaces of 3D objects. They define the orientation of surfaces, play a key role in lighting calculations, and enable smooth shading by interpolating across polygon surfaces. Normals are fundamental for simulating how light interacts with objects and achieving realistic lighting and shading effects in 3D scenes.
NRD#: NVIDIA Real-Time Denoisers (NRD) is a spatio-temporal, API-agnostic denoising library designed to work with low ray-per-pixel signals. It uses input signals and environmental conditions to deliver results comparable to ground-truth images.
Octahedron-normal vectors#: These are a way to encode normals by projecting them onto an octahedron, folding it, and placing it on one square. This gives the normals uniform properties for value distribution and reduces encoding and decoding costs.
Opacity#: This refers to the degree to which an object or part of an object is transparent or allows light to pass through. It is a fundamental property used to control the visibility and transparency of 3D objects and their components within a rendered scene.
Pixel Checkerboard#: This is a technique used to analyze and visualize the distribution of pixel shading workloads across the screen or image. It involves rendering a checkerboard pattern over a scene, where each square of the checkerboard represents a pixel. The color of each square can indicate the complexity or computational workload of the corresponding pixel.
Primary Depth#: This refers to the depth information associated with the primary rays in a ray tracing pipeline.
Primary Ray Bounces#: This refers to the first set of rays cast from the camera or viewer into a 3D scene during the ray tracing process. These primary rays determine which objects or surfaces in the scene are visible from the camera’s perspective.
Primary Specular Albedo#: This refers to the albedo or reflectance value that represents the color and intensity of specular reflections on a surface from direct light sources, such as point lights or directional lights, when using ray tracing or other rendering techniques.
Primitive Index#: This refers to a unique identifier or index assigned to a primitive in a rendering or graphics pipeline. Primitives are fundamental geometric shapes or elements used in computer graphics to construct more complex scenes and objects. These primitives can include points, lines, and triangles. Each primitive is assigned a unique index that allows the GPU to process them individually or in specific groups as required by the rendering algorithm.
ReBLUR#: This is a denoiser based on the idea of self-stabilizing, recurrent blurring. It’s designed to work with diffuse and specular signals generated with low ray budgets. ReBLUR can support checkerboard rendering, producing reasonable results when casting just half a ray per pixel.
ReLAX#: This is a variant of SVGF optimized for denoising ray-traced specular and diffuse signals generated by NVIDIA RTX™ Direct Illumination (RTXDI). ReLAX improves image quality and performance over stock SVGF, preserving lighting details produced by RTXDI light counts and offering better temporal stability and responsiveness to changing lighting conditions.
ReSTIR Direct Illumination#: ReSTIR, or spatiotemporal reservoir resampling, samples one-bounce direct lighting from many lights without needing to maintain complex data. ReSTIR DI samples all primary lighting and shadows in screen space, significantly faster than previous solutions. This screen-space light sampling solution can handle a large number of lights with a small number of rays per pixel.
ReSTIR Global Illumination#: ReSTIR GI resamples multi-bounce indirect lighting paths. At a single sample per pixel every frame, this solution achieves a significant improvement in mean-square error (MSE). Combined with a denoiser, this offers high-quality path tracing at real-time frame rates.
RTX#: RTX represents real-time ray tracing, where the calculations required for ray tracing are performed in real-time, enabling lifelike graphics and dynamic lighting effects in video games and other applications.
RTXDI#: RTX Direct Illumination generates a large number of fully ray-traced dynamic lights, creating photorealistic lighting of scenes that require computing shadows from many area lights. This eliminates the need for baking lighting and using hero lights, unlocking creative freedom even with limited ray-per-pixel counts. When integrated with RTXGI and NVIDIA Real-Time Denoiser (NRD), scenes benefit from realistic and scalable ray-traced illumination and clean, denoised images, regardless of the environment.
RTXGI#: RTX Global Illumination enables multi-bounce indirect light without bake times, light leaks, or expensive per-frame costs. RTX Global Illumination (RTXGI) is a scalable solution that powers infinite bounce lighting in real time, even with strict frame budgets. This technology accelerates content creation with real-time in-engine lighting updates and supports a wide range of DirectX Raytracing (DXR)-enabled GPUs. RTXGI is designed to work in conjunction with RTX Direct Illumination (RTXDI) to create fully ray-traced scenes with a large number of dynamic light sources.
Screen-Space Motion Vector#: (SSMV) is a data representation that captures the motion of objects or pixels between consecutive frames within the screen space. SSMVs are used in various rendering techniques, such as motion blur and temporal anti-aliasing, to simulate realistic motion effects.
Secondary Ray Bounces#: These are the rays that are cast after the primary rays during the ray tracing process. Primary rays are initially shot from the camera or viewer into the 3D scene to determine which objects or surfaces are visible. When these primary rays hit a reflective or refractive surface, secondary rays are generated to simulate additional lighting effects, such as reflections and refractions.
Secondary Specular Albedo#: This refers to the albedo or reflectance value that represents the color and intensity of secondary, or indirect, specular reflections on a surface when using ray tracing or other advanced rendering techniques.
Shading Normal#: Often referred to as a “Geometric Normal,” this is a vector that represents the orientation or facing direction of a surface at a particular point on a 3D object. The shading normal is used in shading calculations to determine how light interacts with the surface and how the surface should be illuminated or shaded.
SIGMA#: SIGMA is a fast shadow denoiser that supports shadows from various light sources. It relies more on spatial filtering than temporal filtering, resulting in minimal temporal lag.
Stochastic Texture Filtering#: Also known as stochastic texture synthesis or stochastic texture generation, this is a technique used in computer graphics and computer vision to create realistic and natural-looking textures. “Stochastic” refers to randomness, and in this context, it involves introducing controlled randomness into texture generation to make them appear more natural and less repetitive.
Tangent#: This refers to a vector that lies in the plane of a 3D surface and is perpendicular to the surface’s normal vector. Tangent vectors are used in techniques like normal mapping and bump mapping to simulate fine surface details and enhance realism.
Texture Coordinates#: These coordinates specify which part of a 2D texture map should be applied to each point on a 3D model’s surface. This mapping enables realistic and detailed texturing of 3D objects, allowing for the application of textures like color, bump maps, and normal maps. By specifying texture coordinates for each vertex, the graphics hardware can interpolate and apply the corresponding texture data smoothly across the entire surface, creating the illusion of complex surface properties and details on the rendered 3D object.
Thin Film Thickness#: This refers to the measurement of the thickness of a thin film or layer of material applied to a surface. This concept is used in computer graphics and rendering to simulate the interaction of light with thin layers of materials, such as oil films on water or soap bubbles.
Tonemapping#: This is a technique for converting high dynamic range (HDR) images or scenes into low dynamic range (LDR) images that can be displayed on screens, while preserving as much visual detail and realism as possible.
Triangle Normal#: These normals define the orientation of a triangle’s surface. They help determine how light rays are reflected or refracted off the triangle’s surface, affecting the appearance of the triangle in the rendered image.
UDIM#: UDIM (U Dimension) is a tile-based texture system where each tile represents a different texture in the overall UDIM texture array. Each tile has its own UV space and its own assigned image.
Vertex Color#: This refers to color information assigned to individual vertices (corner points) of a 3D model or object. Each vertex can have a specific color value, typically represented as a combination of red, green, and blue (RGB) values.
Virtual Motion Vector#: This refers to the motion of objects between frames. These motion vectors help reduce data redundancy and improve compression efficiency by describing how objects move from one frame to another.

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